One of the City's most prominent investors is close to clinching a £550m buyout of his business with the backing of a former owner of Jupiter‎ Asset Management.

Sky News has learnt that Richard Buxton, the chief executive of Old Mutual Global Investors (OMGI), is on the brink of a deal ‎to buy a £25bn chunk of the company.

The management buyout will be backed by TA Associates, a private equity firm which enjoyed success as a shareholder in Jupiter, according to a banking source.

An announcement could come as soon as Friday, although it is more likely next week, the source added.

If completed, the deal would follow an intense bidding war which in‎ recent weeks has included serious interest from Macquarie, the Australian financial services group.

Old Mutual, the FTSE-100 Anglo-South African financial services group, has been holding talks about a sale of the unit headed by Mr Buxton since the autumn.

Sky News revealed in September that the star fund manager was trying to assemble a buyout of its £25bn single-strategy operations, prompting confirmation from Old Mutual that it was "assessing, together with OMGI management, internal and external structures" for the business.

The prospective sale of OMGI's funds arm will not include the multi-asset unit which manages about £11bn.

If a private equity deal does take place, it would leave Mr Buxton in charge of one of the City's most influential independent fund management businesses.

He joined OMGI in 2013 and then became chief executive of the division two years later.

Old Mutual is now being split into four parts by chief executive Bruce Hemphill.

They are: South African lender Nedbank; a US-based asset management business in which Old Mutual's stake will be sold down to 6% later this year; Old Mutual Wealth, which is the unit in which OMGI sits; and Old Mutual Emerging Markets.

Mr Hemphill, the group's chief executive, is a rarity among big company bosses in pursuing a strategy which will lead to him effectively losing his job once the break-up is complete.

He has enjoyed the support of investors for the move, however, as he seeks to unlock the valuation discount typically suffered by conglomerates.

"I don't think it was particularly badly managed or poorly put together, there was just no sense in the structure," Mr Hemphill told The Times recently.

Established in Cape Town in 1845, Old Mutual has endured speculation for years about its corporate structure.

Mr Buxton's move to lead a buyout of OMGI's third-party business has attracted attention given his prominence in the City.

He is one of a small band of star managers whose influence grants him rarefied‎ access to company boardrooms.

It is unclear what the business he will lead will be called, since Old Mutual's name will only remain attached to its South African operations.

If the sale does take place, it will be the latest in a string of significant deals in the asset management industry this year.

The biggest was the £11bn merger of Aberdeen Asset Management and Standard Life to form Standard Life Aberdeen, which completed during the summer.

Hermes Fund Managers, which is owned by the BT Pension Scheme, is also exploring a sale.